“Ike” Bowen studied at the Houghton Seminary and Oberlin College. As a graduate student at the University of Chicago he worked with Robert A. Millikan, whom he accompanied to the California Institute of Technology. There he served as Millikan’s assistant, taught physics, researched cosmic rays, and earned his Ph.D. with an important dissertation on heat losses in the evaporation of water from lakes. His investigation of the ultraviolet spectra of highly ionized atoms led to his identification of the mysterious “nebulium” spectral lines of gaseous nebulae as forbidden lines of ionized oxygen and nitrogen. He soon explained most of the lines of gaseous nebulae. During World War II he was in charge of photographic work on the rocket project at the Jet Propulsion Laboratory. As director of the Mt. Wilson Observatory from 1946 to 1948 and of the combined Mt. Wilson and Palomar Observatories from 1948 to 1964, he directed the completion of the 200-inch Hale telescope and 48-inch Schmidt telescope and designed many of their instruments, including a novel spectrograph. He also initiated baking photographic plates to improve their sensitivity. He continued designing astronomical instruments after his official retirement.